Safety system



June 9, 1931. KNOWLES 1,809,280

SAFETY SYSTEM Filed lay 26,- 1928 2 Sheets-Sheet l lNVENTOR flewey fl Know/es.

- A'IFTORNEY June 9, 193i.

D. D. KNOWLES SAFETY SYSTEM Filed May 26, 1928 2 sneewsneet -2 INVENTOR flewey D Know/ea B ,4

WATTORNEY Patented June a [1931 UNITED STATES DEWEY n. xnowrns, or roims'r nuns noaoucn, rmmmvama, assrenon r WESTINGHOUSE ELECTRIC & MANUFACTURING PENNSYLVANIA.

Application flled Iay 26, 1928. Serial No. 280,710.

g This application is a continuation in part and in part a substitute for my application Serial No."164,625, filed January 29, 1927.

My invention relates to safety control sysl tems. and particularly to control systems intended for use in connection with furnaces using a liquid or gaseous fuel.

On'e object of my invention is to provide a safety system that will be actuated by a failure of the fuel-supply pressure and will so operate as to prevent the accumulation of unburned fuel in the furnace upon renewal of the fuel-supply pressure.

Another object of my invention is to provide a safety control system that'shall be controlled bya flame of the burning fuel.

.Another object of my invention is to provide a safety control system that shall be controlled by, and in accordance with, the

a conductivity of an ionizable gap.

Another object of my'invention is to provide a safety control system that shall be controlled by, and in accordance with, the conductivity of an air gap subjected either directly or'indirectly to the flame of a furnace or toa fluid medium.

. Another object of my invention is to provide a safety system actuable in accordance with the conductivity of a gap normally subjected to a movin terruption of the %ow of the medium.

Another object of my invention is to provide a safety system that 'will disconnect a furnace fuel-supply system or other apparatus from a source of liquid or gaseous fuel upon failure of a flameof the furnace.

f A still further object of my invention is to provide a stem of the class described that shall be 0 such a character as to retain the instantaneous-operation feature throughout its entire life and under substantially all ordinary conditions of operation of a furnace.

In practicing my invention, I rovide a sarmv srs'rm fluid medium upon in-'.

COMPANY, A OORPOBA'I'ION QI' REISSUED tion, as practiced at present, I associate With the electrodes defining an ionizable gap the conductivity of which is to be measured by .an electric-discharge device, the operation of which is controlled by the direct conductivity of the flame or by the conductivity of a gap. However, in its practice, my invention is not necessarily limited to the use of such an electric-discharge device.

In the drawings: Figure l'is 'a view, partly diagrammatic and partly sectional, of a furnace heater equipped with a preferred embodiment of my invention. a

Fig. 2 is a diagrammatic view of an altero5 native form of my invention.

Fig. 3 is a view partl' diagrammatic and partly sectional, of a stlll further modification of a device embodying my invention, and

Fig. .4 is a view, partially diagrammatic and partially in side elevation, of another modification of a device embodying my invention.

Referring more articularly to 1 of the drawings, a fiirn'aoe or heater 11 is. provided with a mobile-fuel-supply line 13 and a plurality of burners 15.

A supply line 13 feeds also a 17 which is usually continuous.

A 'd glow tube 19" is operatively associate with the furnace 11 and comprises a container or casing 21', a cathode 23, an

pilot flame anode 25 and a control grid 27. v A conductor 29 is connected .to'thegrid 27 and extends, through an insulating bushing 31 in a wall of the furnace, into the mally occupied b the upper end of the ilot flame 17. he inner end of the con uctor 29 is, of course, connected to a suit-" able electrode material capable of withstanding contiuuously the high temperature of a flame." The anode 25 is connected, by a conductor 33, to a-second electrode having its inner end located in the space occupied by the lower end of the flamed], an insulat. ing bushing 35, similar to the bushing 31, being provided therefor. Instead of connecting the anode 25 to an electrode as just ribed, the aning n i m y be we space nornected, either conductively or capacitatively,

' to the fuel-supply line 13 with substantially as good results I preferably make the.

When an alternating potential is impressed between the anode and the cathode, no current will flow therebetween, as the grid is effectively insulated, but upon establishinga grid leakage path, t e tube will 'ionize, and a substantially rectified current will flow in the output circuit thereof.

An output circuit is connected between the cathode 23 and the anode 25 and comprises an actuating solenoid 37, a resistor 39 and the secondary winding 41of a transformer 43. The primary winding 45 of the transformer is connected to a source 47 of alternating current.

A core member 49* of magnetic material cooperates with the coil 37 and is suspended from an arm 51 which is permanently connected to a fuel-s'u ply-controlling valve 53 interposed in the filel-supply line 13. a The arm 51 is extended beyond its point of connection with the valve, and a heavyweight 55 is connected to the other end thereof.

Referring more particularly to Fig.2 of. the drawings, a thermionic tube 61 has a filament 63, a grid 65 and a plate 67 which is so arranged and connected to the winding of a highly sensitive relay 69 as to include,

1n the output circuit thereof, in series-cir-' cult relat on, a source 71 of direct current potential.

A self-locking valve-operating mechanism 73 is controlled by the relay 69. The valveoperating' mechanism 73 may comprise a' pinion 75 rigidly mounted on the-stem of a.

valve 77 and having associated therewith an actuating rack 79 provided with an exten;v s1on 81 plvotally connected to a lever 83.

The lever 83 has a fulcrum 85 intermediate the point of its connection with the link 81 and a handle 87 which projects beyond a protect on casing89. A spring 91 is .con-

,nected between the end of the lever oppos te to the handle 47 and to the casing and tends toso move the lever 83 as to maintain the valve 77 in its closed position.

A movable latch element 93 is pivotally connected to, .and carried by, the extension 81 and cooperates with amovable detent or latch 95 ;.to retain the valve in its closed position. The latch 95 is connected to a bell to ground. The control grid of the grid crank 97, one arm 99 of which has-a biasing spring 101 connected thereto, and which may also be controlled by an electromagnet 103. The electromagnet is energized from a suitable source 105,vthe circuit being controlled by a switch arm 107 and a fixedcontact member 109, associated with, and controlled by, the relay 69. A biasing battery 111, in series with a grid-leak resistor 113, is con nected between the grid and the filament 63 of the tube and biases the grid negatively with respect to the filament. A conductor 115 is connected to the grid 65' and to one terminal of the resistor 113, as well as to an insulated electrode 117, projecting through a wall of the furnace, the inner upper portion of the space normally occupied by a pilot flame 119. The filament 63 of .the tube is connected to'a metallic portion 121 of the 'pilot burner through a biasing battery 123, the battery serving to impart a positive potential to the flameionized path and, consequently, a positive potential to the grid 65 when the flame is burning. Asource of electric potential 125 energizes the filament 63.

Referring more particularly to Fig. 3 of the drawings, 1' have here illustrated another form of furnace and fuel-supply mechanism comprising .a metal furnace casing 131,'having associated therewith an air pressure device 133 driven by an electric motor 135. The device 133 ,may be any positive pressure blower usually emplo ed in connection with oil burners and is e ective to force a quantity of oil through a supply conduit 137 to be atomized by suitable means well known in the art andto burn within the furnace casing 131. .At the same time, air is supplied, under pressure, within the conduit 139, whereby a highly effective flame is obtained within the furnace casing131.

A'supply circuit for the control system and for the motor may comprise conductors 141 and 143, the supply of e ergy from which tov the motor. and to th safet sysknown in the art. A relay in the supply circuit to the motor comprises a coil 147, a core 149, having associated therewith a contact bridging member 151 and suitable substantially fixed contact members. 7

A' grid. glow tube 153, of the kind described in detail inconnection with Fig. 1 of the drawings, is provided and has its cathode connected to one terminal of thev ary winding 155 is connected to the anode of the grid glow tube and is also connected tem is controlled by protecting devices wellv end of the electrode being located in the comprises a. primary winding 163, the usual core member and a secondary winding 165.

One terminal of the secondary Winding 165 is connected to ground while the other terminal thereof is connected to a suitable ignition device 167, usually constituted by a spark gap. Y

The primary coils or windings 158 and 163 are connected by suitable conductors to the supply-circuit conductors 141 and 143.

Referring to Fig. 4, I have there illustrated another modification in which a control air gap is located in the stack or flue 171 of a'furnace 173, which is supplied with mobile-fuel througha supply pipe 175. A valve 177 is connected in the pipe and is held in the open position by the action of a core 179 connected to one end of a. lever 181 mounted on the valve stem, a relatively heavy weight 183 being. connected to the other end of the lever. An electric discharge device 185, as hereinbefore described, has its anode connected to one electrode 187 located in the stack or flue. A second electrode 189 cooperates with the electrode 187 to define a gap the conductivityof which is affected by the products of combustion of the furnace, and is connected to the control electrode of the device 185. The cathode of they device is electrically connected to one terminal of -a secondary coil 191 of a transformer the primary ergized from a suitable source of potential coil 193 of which is en- (not shown). The other terminal of the secondary coil 191 is electrically connected toone terminal of a relay coil 195 associated with the core 17 9.

Referring more particularly to Fig. 1. of

the drawin it is assumed that the pilot operatively flame is burnin and that the transformer 43 is energized, w ereby the grid glow tube 19 is energized between the cathode and the anode. As is pointed out in my co-pending prior application, a discharge will be maintained in the tube so long as a leakage path is maintained between the anode and the grid, and, in Fig. 1 of the drawings, this leakage path-is provided more particularly by the pilot flame. I have found that the conductivity of a flame is sufliciently high to prevent the, accumulation of a blocking charge on the grid 27 of the tube so that, as long as the pilot flame is burning, a current will flow in the circuit including the anode and cathode of the tube, the coil 37, the resistance 39 and the secondary winding 41. V The resistance of the resistor 39 is so selected that the current traversing the coil 37,

as long as the pilot flame is burning, is just fore, very remote.

age path provided thereby between the grid electrode and the anode of the grid glow tube would be no longer present and the grid 27 would acquire a sufliciently high negative charge to stop the discharge between the anode and the cathode, all as explained in my application Serial N 0. 149,290. As soon as the glow discharge between the anode and the cathode ceases, the coil 37 is, of course, deenergized, whereby the weight is permitted to drop and to close the valve to shut ofl any further supply of fuel.

It is, of course, obvious that, when the coil 37 is not energized, the valve 53 cannot be kept open except by manually holdingthe core 49 down against the action of gravity onthe weight 55, and the likelihood of the furnace being filled with unburned fuel when the pilot flame is not burning is, there- While Fig. 1 shows the use of a grid. glow tube in combination with a safety control system, I have found that an ordinary thermionic amplifying device may be used, particularly in places Where an alternatingguished, for any reason whatsoever, the leakcurrent supply of electric energy is not available. Such a system is shown in 2 of the drawings. By suitably adjusting the voltage of the biasing batteries 113 and 123, the potential of the grid 65 may be maintained so long as the pilot flame 119 is burning.

As is well known in the art, a positive bias on the grid of a thermionic tube permits the flow ofv space current, and this current is utilized-to energize the relay 69 whereby to maintain the contact arm 10 in engagement with-the contact member 109.

So long as the arm 107 is in engagement with the contact member 109, the electromagnet 103 is energized and detent 95 is maintained out of engagement with the latch 93, permitting manualdepression. of the lever 83 and, consequently, opening of the valve 75. After having been manually moved, the lever ;.83 will be maintained in its .depression position against the action of the spring 91 by the electromagnet 103, thus keeping the valve 77 open so long as the electromagnet 103 is energized.

Upon extinction of the-pilot flame, grid-bias balance is destroyed, the grid being then biased negatively by the battery 111 to a potential sufiicient to block the tube and the ' metal casin stop the current in the relay 69. Switch arm 107 is then moved to disengage contact 109, whereby clectromagnet 103 is deenergized and valve 77 is permitted to close un- 1 der the action of spring 91, the movable de tent 95 being moved to the left into operative positionunder the influence of spring 101.

In its downward travel, the latching element 93 passes by the end of the latch or detent 95, and the subsequent engagement of member- 93 withthe: under portion of the member. 95 prevents the extension 81 and, therefore, the rack bar 79, from being raised by the lever 83 'until the detent 95 is movedtoward the tight by the action of electromagnet 103. y a

i It is thus apparent that, by utilizing my invention in connection with gas or oil-fired furnaces or thelike, it will be substantially impossible for a careless workman to open the main fuel-supply valve and to leave it in oil isforced into the casing 131 in an atomized condition and is ignited by the ignition device 167 in a manner well known in the art. The electrode 159 is so located as to project into the flame and a conducting or grid leakage path is, therefore, provided between the grounded anode of the grid glow tube 153,the usually more or less grounded 131 and the electrode 159, the outer end 0 which is connected to the control grid of the tube153. The conductivity of the flame of the burning fuel is sufficiently high. to provide the proper grid leakage path so that a current will traverse the coil 147 as long as the electric system is energized and as long as a flame exists"with-' in the burner casing 131. It is obvious that a shunt circuit to the relay contacts normally brid ed by member 151, should be in-' cluded in t e system, to permit of starting up the system and a conductor 197 is shown as bein provided for this purpose. As this part 0 the system constitutes no part of my invention, it is not illustrated or described in detail. If,, for any reason, the supply of an atomized mobile fuel should be interrupted, as may happen in case of a slug of water occurring in the pipe line, theffiame would be extinguished and .the tendency of the room thermostat would, ofcourse, be 'to remain closed for a certain length of time, which may be as much as 60 .seconds, during which time the motor would continue to operate and a sup ly of atomized fuel might collect in the burner casing 131. As

soon asthe-flame is extinguished, however,

mobilefuel in case of the grid leakage'p'ath will no longer exist, I

so that the current traversing the coil 147 of the control relay will be interrupted within a few seconds, whereby the motor-control circuit is opened and the motor is shut down.

The initial control means is thus a normally continuously energized closed-circuit means, WhlCll is, also, a voltage-responsive means.

While Figs. 1 and 2 show the use of a.

pilot flame as constituting a conducting path between two electrodes connected, respectively, to a control grid and another electrode of the electrical discharge device, it is possible also to use the main flame of the burning fuel t0 provide this conducting path, and this is illustrated in Fig. 3.

However, the device embodying my invention is not restricted to the use of a flameionized path or gap located between, and

defined by, a pair of spaced electrodes. I may use any portion of the space either in the combustion chamber normally ionized by the combustion products and substantially deionized upon the cessation of the main .flame or I may locate the electrodes defining an ionizable gap at any place where the gap is subjected to the actionof the flame or of the products of combustion thereof,

the main requisite being that the gap is ionized to a suflicien't extension to increase its conductivity to such value as will permit a current to flow therethrough to operate the control-circuit means. Such location is shown in Fig. 4 of the drawings.

It is, of course, obvious that it is notalways necessary to employ two special electrodes, as shown in Figs. 1 and 4. Only one special electrode may be utilized, as shown in Figs. 2 and 3, the other electrode being constituted by the pipe 121 in Fig. 2

or by the grounded casing 131 of Fig. 3. Y

My invention is also applicable to systems ofany type which require the constant fiow' ofa cooling fluid, lubricating oil orthe like. If, for example, it is desired to guard against thefailure of cooling water circulation in distilling apparatus, condensers, refrigerating machines, bearings or thelike, the control electrodes of Fig. 1 of the drawings may be immersed in such liquid at any suitable location. In case of cessation of flow of'the liquid, the leakage path would be interrupted, that is, the conductivity thereof would be greatly reduced and substantially the same control effects would be obtainable as has been hereinbefore set.

forth in regard to sto ping the 'su ply of Failure ofa ame of the burning fuel. Such cessation of 'the flow of a cooling fluid and operation of a control system and circuit associated therewith could be used to deenergize other elements and the system or to place them in an inoperative position to prevent danger thereto which might occur in case of continued operation thereof during the time that the flow of cooling liquid is interrupted. The electrodes connected to conductors 29 and 33 shownin Fig. 1 may be so located as to project into supply pipe 13 but suitably insulated therefrom, whereby the same results hereinbefore described would be obtained in case of failure of the oil supply.

As my invention, in its broadest aspects,

is not limited-to a control valve or even to an electric motor, I preferto use the hrase an actu'able means to designate the evice, appliance, or system, which is controlled or actuated by, and in accordance with, my invention.

I have elected to show the operation of an electrical discharge device in connection with a safety system for electric burners and have also shown and described specific locations of the electrodes in connection therewith. Obviousl my system is not limited thereto and may make modificae tions therein without invading the field of the pertinent prior art, and I desire, there- .fore, that the appended claims shall be limited in scope only as demanded by such prior cluding said main electrodes, source of potential and fuel-flow-controlling means, a pair of conductors making contact with the flame of said pilot burner and connections between one of said conductors and one of said main electrodes and between the other of said conductors and said control electrode.

2. In a fuel-supply system of the type including a fuel burner and means for supplyirtlg fuel thereto, a current-controlled shut- 0 means for said fuel-supply means, conductin terminals positioned in thepath of flow o the products of combustion of said burner, an electric-discharge'device having main. electrodes and a control electrode,

means for including said main jelectrodes in circuit with said shut-off means and a source'of voltage, and conductors connecting one of said terminals to one of said main electrodes and the other said terminal to said control electrode.

3. In a fuel burner system of the type ineluding afuel-supply means and a shut-off device therefor, current-controlled means for controlling said shut-off device, including a gaseous electric-discharge device having main electrodes and 'a control electrode between them, said main electrodes being connected in series with said current- I controlled means and a source of alternating voltage, and conductors, connected respectively to said control electrode and one of said main electrodes, electrically con- ;recized by contact with the flame of said 4. In a fuel burner of the type including a fuel-supply means, an electrically actuated control means for maintaining fuel flow through said fuel-supply means and'a normally-closed-circuit, including an electricdischarge device having a casing having a plurality of main electrodes and a control electrode within it, said principal electrodes being in circuit with said control means and a source of voltage, said control electrode being connected to a conductor positioned in the path of flowofthe products of combustion of the burner, and one of said main electrodes being connected to another conductor positioned in said path. a

- 5. In combination with a burner, means for controlling the flow of fuel thereto and spaced electrodes positioned in the path of flow of combustion products from said burner, electrical means operative when combustion products from said burner contact said electrodes to cause between said electrodes an electric discharge so minute as to be incapable of igniting fuel and as a result of such discharge to render operative said fuel controlling means.

6..In combination with a burner, means for controlling the flow of fuel thereto, a

pilot burner for igniting said fuel, and

spaced electrodes positioned in the path of flow of combustion products from said pilot burner, electrical means operative when combustion products from said pilot burner contact with said electrodes to cause between said electrodes an electric discharge so minute as to be incapable of igniting fuel and as a result of such discharge to simultaneously render operative said fuel controlling means.

'7. In combination with a burner, means for-controlling the flow of fuel thereto and 'spaced'electrodes positioned in the path of flow of combustlon products from said burner, electrical means operative when combustion products from said burner contact said electrodes to cause between said electrodes an electric discharge so minute as to be incapable of igniting fuel and for amplifying said discharge and as a result of such discharge to render operative said fuel controlling means. I

8.- In combination with a burner and electrically o erated means for controlling the flow of el thereto, an electrical control device' normally operative to block current flow in circuit with'said electrically oper ated means and a source of electrical power; asecond circuit including said control device, and spaced electrodes positioned in the path of flow of combustion products from said burner whereby combustion products contacting said electrodes will cause an elec- A trio discharge betvveen said electrodes so minute as to be incapable of igniting fuel, which discharge renders said control device operative to permit current flow.

In testimony whereof, I have hereunto subscribed my name this 22nd day of May, 1928.

a 10 DEWEY D. KNOWLES. 

